Weight Loss Exercise: HIIT for Fat Loss

When you ask most trainers about effective cardio training for fat loss, they will probably tell you to run/row/swim with low intensity for at least 30 minutes. One main argument for this advice is that your metabolic system changes its main energy source from glycogen (carbs) to fat after approximately 20 minutes of low-intensity training and then your body starts to burn fat as fuel. We believe otherwise.

According to our research, more and more studies indicate that low-intensity cardio training is NOT what gives you the best results. It turns out that sprints, frequent changes of tempo, other high-speed intervals (together referred to as high-intensity intervals) and shorter training sessions (maximum 1 hour) are way more effective for losing body fat and increasing overall fitness. The positive effects of cardio training on your health are an improved cardiovascular system, which you can achieve faster when you use high-intensity interval training (HIIT), instead of long, slow runs. This will also help save time. At least 20 minutes of HIIT (e.g. some sprints with short walking periods in between) is better than 40 minutes of slow jogging.

Similar to strength training, your body adapts better and faster to HIIT. If you work out with very high resistance, you will see an increase in strength after a short period. If you work out with low resistance, your results won’t amaze you that much. The same principle applies to cardio training.

Some newer studies have shown that you will not only be able to run faster, but also longer if you follow HIIT. To make this clearer to you, this means that you can also improve your personal 5 km (3 mi 188 yd) record more effectively by performing 20 minutes of HIIT (e.g. 10x200m sprints with walking periods in between, 3 times a week) for 4 weeks, instead of doing slow endurance runs three times per week for an hour.

HIIT also has a positive impact on muscle growth. If you have ever seen a track and field competition you might have recognised that sprinters, who naturally do a lot of interval training, are very muscular, while marathon runners, who include long endurance runs as part of their workouts, are mostly slim and unremarkable. One reason for that is that during a high-intensity interval workout, your whole body is under high tension (the adaptation effects are similar to the effects of high-resistance strength training). But, are long endurance runs optimal for burning more fat? Or is HIIT the best option?

Answer: HIIT wins again

Admittedly there is enough evidence to say, that average people, do reach the fat burning zone after 20 minutes, but the amount of fat burned as energy during low-intensity cardio sessions stays on a low level. You won't get in the efficient fat-burning zone with HIIT, but you will burn so much more energy (calories) that your body is forced to burn a huge amount of fat afterwards because your glycogen storages will already be empty after the cardio session (and, as you know, the human body still needs energy for living, adaptation after workouts and so on). There's one more effect that helps you burn even more energy and fat AFTER your training session, the after burn a.k.a. EPOC (excessive post-exercise oxygen consumption). During a HIIT workout, your body will be in an anaerobic zone for most of the HI-time where oxygen is in short supple and your body produces lactic acid due to a second way of energy supply (without the use of oxygen). This energy from anaerobic exercises lasts for just a few seconds (up to 20-40 sec). After your HIIT training your body contains a lot of lactic acid which it has to remove with effort.And this is the reason why you burn additional energy after the session. So you have a higher energy consumption during the session and also a few hours afterwards...sounds great, doesn't it?